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<h2><span class="refentrytitle">Macro BOOST_VMD_ASSERT</span></h2>
<p>BOOST_VMD_ASSERT — Conditionally causes an error to be generated. </p>
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<h2 xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv-title">Synopsis</h2>
<div xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv"><pre class="synopsis"><span class="comment">// In header: &lt;<a class="link" href="variadic_macro_data_reference.html#header.boost.vmd.assert_hpp" title="Header &lt;boost/vmd/assert.hpp&gt;">boost/vmd/assert.hpp</a>&gt;

</span>BOOST_VMD_ASSERT(...)</pre></div>
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<a name="idm11248"></a><h2>Description</h2>
<p>... = variadic parameters, maximum of 2 will be considered. Any variadic parameters beyond the maximum of 2 are just ignored.</p>
<p>The first variadic parameter is:</p>
<p>cond = A condition that determines whether an assertion occurs. Valid values range from 0 to BOOST_PP_LIMIT_MAG.</p>
<p>The second variadic parameter (optional) is:</p>
<p>errstr = An error string for generating a compiler error when using the VC++ compiler. The VC++ compiler is incapable of producing a preprocessor error so when the 'cond' is 0, a compiler error is generated by outputting C++ code in the form of:</p>
<pre class="programlisting"><span class="keyword">typedef</span> <span class="keyword">char</span> <span class="identifier">errstr</span><span class="special">[</span><span class="special">-</span><span class="number">1</span><span class="special">]</span><span class="special">;</span>
</pre>
<p>The errstr defaults to BOOST_VMD_ASSERT_ERROR if not supplied. It is only relevant for VC++.</p>
<p>returns = If cond expands to 0, this macro causes an error. Otherwise, it expands to nothing. For all compilers other than Visual C++ the error is a preprocessing error. For Visual C++ the error is caused by output invalid C++: this error could be masked if the invalid output is ignored by a macro which invokes this macro. </p>
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